Why null is shown when a file is read ?

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why null is shown when reading from a file.
the value inserted are q-1-q-true
but the values shown are nullq-null-nullq-nulltrue
The code given below:-

Scanner sc1=new Scanner(fr);
				while(sc1.hasNextLine())
				{
					char []p=sc1.nextLine().toCharArray();
					char [] a=new char[p.length];	
					for(int i=0;i<p.length;i++)
					{
						if(p[i]!='-')
						{
							if(String.valueOf(p[i])==(null))
							{
							}
							else
							{
							a[i]=p[i];
							col[x][j]+=p[i];
							}
							
						}
						JOptionPane.showMessageDialog(null,"col "+col[x][j]+":"+ j);
						//procedure pr=new procedure();
						
						if(p[i]=='-')
						{
							j++;i++;
						}
					}x++;
				}
				sc1.close();n=0;j=0;int y=0;

What I have tried:

File fo="c:\Tables";
for(File fr:fo.listFiles())
{

Scanner sc1=new Scanner(fr);
				while(sc1.hasNextLine())
				{
					char []p=sc1.nextLine().toCharArray();
					char [] a=new char[p.length];	
					for(int i=0;i<p.length;i++)
					{
						if(p[i]!='-')
						{
							if(String.valueOf(p[i])==(null))
							{
							}
							else
							{
							a[i]=p[i];
							col[x][j]+=p[i];
							}
							
						}
						JOptionPane.showMessageDialog(null,"col "+col[x][j]+":"+ j);
						//procedure pr=new procedure();
						
						if(p[i]=='-')
						{
							j++;i++;
						}
					}x++;
				}
				sc1.close();n=0;j=0;int y=0;

Posted 12-Mar-23 20:34pm

Member 12712527

Updated 12-Mar-23 21:37pm

v3

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OriginalGriff · Answer 1 · 2023-03-12T21:37:00

Without access to your files and file system as input, we can't really tell.

So, it's going to be up to you.
Fortunately, you have a tool available to you which will help you find out what is going on: the debugger. How you use it depends on your compiler system, but a quick Google for the name of your IDE and "debugger" should give you the info you need.

Put a breakpoint on the first line in the function, and run your code through the debugger. Then look at your code, and at your data and work out what should happen manually. Then single step each line checking that what you expected to happen is exactly what did. When it isn't, that's when you have a problem, and you can back-track (or run it again and look more closely) to find out why.

Sorry, but we can't do that for you - time for you to learn a new (and very, very useful) skill: debugging!